Safety device against leakage from ships, especially tankers

ABSTRACT

A ship such as a tanker for the transport of oil and oil products, is provided with a safety device to prevent leakage of the product being stored or transported. The safety device comprises a shield which preferably is flexible and extends along the ship&#39;&#39;s hull in spaced relation thereto so as to define vertically extending narrow spaces at the inner side of the hull. Said narrow spaces are opening in the bottom region of the ship and shall when the ship is used contain a liquid having the same or a higher density than the transported product. As an example the product may rest on a bed of water at the ship&#39;&#39;s bottom, water than also being present in the said narrow spaces. If for instance due to a collision a hole is formed in the ship&#39;&#39;s hull the liquid level in the actual narrow spaces will be adapted after the sea level whereby the level of the product in the cargo space takes a balanced position in which leakage of the product is prevented. As an alternative to water the transported product proper may be contained in the narrow spaces in which case a small leakage may occur if the hull of the ship becomes damaged.

Ilnited States Patent [1 1 Backstrom 1 ,Ian. 15, I974 Arne L. Backstrom, Stockholm, Sweden [75] Inventor:

[73] Assignee: Svenska Entreprenad AB Sentab,

Stockholm, Sweden [22] Filed: Nov. 118, 1971 [21] Appl. No.: 199,998

[30] Foreign Application Priority Data Nov. 23, 1970 Sweden 15866/70 [52] US. Cl 114/74 R, 220/9 A, 220/13 [51] Int. Cl B631) 25/12 [58] Field of Search 114/74 R, 74 T, 74 A,

114/0.5 T, 72, 73, 68, 69; 220/85 A, 85 B, 63 R, 63 A, 9 A, 9 LG, 13; 174/51 Primary Examiner-Trygve M. Blix Assistant Examiner-Donald W. Underwood [57] ABSTRACT A ship such as a tanker for the transport of oil and oil products, is provided with a safety device to prevent leakage of the product being stored or transported. The safety device comprises a shield which preferably is flexible and extends along the ships hull in spaced relation thereto so as to define vertically extending narrow spaces at the inner side of the hull. Said narrow spaces are opening in the bottom region of the ship and shall when the ship is used contain a liquid having the same or a higher density than the transported product. As an example the product may rest on a bed of water at the ships bottom, water than also being present in the said narrow spaces. If for instance due to a collision a hole is formed in the ships hull the liquid level in the actual narrow spaces will be adapted after the sea level whereby the level of the product in the cargo space takes a balanced position in which leakage of the product is prevented. As an alternative to water the transported product proper may be contained in the narrow spaces in which case a small leakage may occur if the hull of the ship becomes damaged.

6 Claims, 11 Drawing Figures PATENTEDJAH 15 I974 SHEET 1 BF 2 Fig. 3a

SAFETY DEVICE AGAINST LEAKAGE FROM SHIPS, ESPECIALLY TANKERS The present invention refers to a safety device having the purpose to eliminate or reduce the risk of leakage from ships, especially tankers for the storing or transport of oil or oil products.

Previously proposed protective arrangements in tankers have as a rule involved that the oil has been stored in containers made of steel, plastics or the like enclosing the oil, being in general free from the ships hull and designed to be completely sealed.

When the containers are made from, for instance, steel,'they must be constructed to withstand total outer water pressure as hydrostatical balance between water on the outside of the containers and oil within the containers is either not envisaged or possible to maintain by means of complicated automatic equipment only. A rigid inner container is, however, easily subjected to damages at a collision or if the ship runs aground the very contingencies which have motivated its construction in the first place and necessitates too high costs in relation to the protection being possible to obtain.

It has also been proposed before to use separate containers made of a plastic cloth hanging or supported in the ship and in some cases surrounded by water. At the filling of the container the initially unfilled bladder is successively developed and the corresponding amount of water is replaced. This arrangement is expensive and the actual degree of filling of the plastic container is a safety device according to the invention as compared with a corresponding conventional tanker design.

FIG. 1 is a cross-section of a tanker provided with a safety device according to the invention.

FIG. 2a is a cross-section according to FIG. I after the occurrence of a damage close to the water line.

FIG. 2b is a cross-section of a conventional tanker after the occurrence of a damage to the same place as difficult to determine. The shape variations of the plastic containers occurring at the filling and emptying operations involve the risk of damage to joints and scams therein.

The present invention has for its object at low cost to substantially eliminate the risk of leakage from ships, especially tankers, which at accident for instance by a collision or when the ship runs aground obtains holes or cracks in the hull.

The safety or protection device according to the present invention which fulfills this object comprises a shield means which extends along the side of the ships hull in spaced relation thereto so as to delimit the cargo space from a vertically extending space along the inner side of the hull, said space opening at the bottom region of the ship and, when the ship is used for storage or transport, being intended to contain a liquid having the same or a higher density than the stored or transported product so that the product will communicate with the liquid in the space.

The only result from a hole in the ships hull will be that the liquid level in the actual narrow space is adjusted to the outer water level whereby the level of the product stored in the cargo space takes a balanced position in which leakage of the product might be completely or substantially prevented.

As will be evident from the description given below, the stored or transported product proper may be contained in the narrow spaces as an alternative to, for instance, water or another liquid having the same or a higher density than the product.

Further features and advantages obtained from a safety device according to the invention will be evident from the detailed description of some embodiments thereof given below. The description is made in connection with the attached schematic drawings which illustrate some embodiments of tankers provided with in FIG. 2a.

FIG. 3a is a cross-section of a tanker having a safety device after the occurence of a damage a small distance above the ships bottom.

FIG. 3b is a cross-section of a conventional tanker after the occurrence of a damage to the same place as in FIG. 3a.

FIG. 4a is a cross-section of a tanker provided with a safety device after the occurrence of a damage to the ships bottom.

FIG. 4b is a cross-section of a conventional tanker after the occurrence of a damage to the same place as in FIG. 41:.

FIG. 5 shows a tanker having a safety device according to the invention in which the narrow spaces contain the product transported by the tanker before and after occurrence of a damage.

FIG. 6 is a cross-section of a modified tanker provided with a safety device according to the invention having three adjacent cargo spaces delimited towards each other.

FIG. 7 is a perspective view of a portion of a tanker provided with a safety device according to the invention.

FIG. 8 is a perspective view showing a detail of FIG. 7.

Referring to FIG. 1 the deck of a tanker according to the invention is indicated 1. Necessary equipment for the filling and emptying of the cargo space 10, gasvents etc. has not been shown. The outer hull of the ship is denoted 2, whereas 3 indicates shields hanging down from the ships deck. Said shields 3 delimit the cargo space 10 from narrow spaces or chambers 4 extending along the sides of the ship and opening in the ships bottom region. The outer water level is denoted 5 and the transported product such as oil is denoted 6. The product rests on a bed of water 7 communicating with water contained in the spaces 4. Its upper level depends on the degree of filling of the container and the relation between the density of the stored product and water, respectively. The shields 3 are exposed to an outwardly directed pressure towards the narrow spaces 4 directed pressure which also depends on the differences in density between the stored product and water and as a maximum amounts to between 3-25 percent of the oil pressure against the water bed(a rather heavy fuel oil and gasoline being considered, respectively). The pressure acting on a shield is transmitted to the hull via substantially vertically extending supports such as suitably designed frame ribs between which the shield which preferably comprises a thick rubber or plastic fabric is freely stretched or possibly in the desired extent bears on the steel plates of the hull. The cargo spacelt) is divided into adjacent compartments longitudinally of the ship by cross-wise extending bulkheads 11, and the shields 3 are sealingly connected to the bulkheads 11 where they come together.

In FIG. 2a there is shown that a hole 8 in the hull for instance as a result of a collision has the only effect that the water level in the adjacent space 4 is adjusted to the outer water level, the level of the stored product being adjusted so as to take a balanced position without any leakage.

FIGS. 2a, 3a and 4a illustrate in comparison with FIGS. 2b, 3b and 4b the variations as regards the risk of leakage at different types of damages to a ship comprising a device according to the invention and being of conventional design, respectively. The damage which may be caused by a collision or if the ship runs aground is in all figures denoted 8 and is in the different figures supposed to have occurred a small distance below the water line, a substantial distance below the water line and at the ships bottom, respectively. The letter P indicates a ship comprising a device according to the invention whereas the letter K indicates a hull of conventional design. Index numbers 1 and 2 at the letters P and K denote the balanced state before and after the occurrence of the intimated damage, respectively. Letter U denotes approximate actual leakage after a damage when a new state of equilibrium has been reached.

These examples illustrate that in a conventional ships design every type of damage will result in leakage of the transported product from complete or total leakage when there is a hole at the water line to a relatively small leakage when there is a hole in the bottom of the ship.

In a ship comprising a device according to the invention there will be no leakage in any of the illustrated cases provided that the shield delimiting the actual narrow space remains intact. However, as the shield will be exposed to only moderate pressures it may be fabricated as mentioned above from a flexible material such as a heavy rubber or plastic cloth or fabric hanging down from the deck. The flexibility or elasticity of the fabric will substantially reduce the risk of damage to the shield.

In the embodiment illustrated in FIG. 5 a water bed for the product is lacking. In the narrow spaces 4 the product transported in the ship is to be found instead. The shield is then normally not exposed to any pressure and might be substantially unsusceptible to damages at for instance a collision. When the outer hull has been damaged, however, it is in this case necessary to calculate with leakage of a small volume of the product corresponding to a certain portion of the volume of the narrow space.

Theoretically the narrow spaces may have a very small width up to the lower limit where laminar flow therein always will be granted. In practice the shape of the narrow space will depend on the design of the strengthening ribs required in the lateral sides of the ship. However, if the spaces are narrow and contain as little volume as possible the amount of liquid in the liquid bed will be kept low.

In FIG. 6 there is shown an embodiment of the invention in a tanker in cross-section having its cargo space divided into three adjacent compartments. The safety device is used in the lateral compartments only which are outwardly defined by the shields. As will be evident from FIG. 6 the shields 3 extend into the region of the ships bottom, i.e., to the deepest part of the ships lateral cargo spaces, for instance, in order to avoid undehave a corresponding protection device below the compartment of the cargo space situated centrally of the ship.

In FIG. 7 there is shown a perspective view of a part of a tanker provided with a safety device according to the invention and transporting a product 6 on a bed of water 7. Water is also present in narrow spaces 4 delimited from the cargo space 10 by means of shields 3 extending along the sides of the tanker and opening at the bottom thereof.

FIG. 8 illustrates a part of a shield 3 which may be fabricated by a rubber or plastic cloth. In order to avoid the risk that static electricity is generated the shields are provided with a wire grating 12 having a ground connection to the hull of the ship.

The shields 3 may also be made ofa metal preferably having good flexibility such as steel.

A safety device according to the invention may equally well be adapted to ships having a double hull. The shields 3 may then be provided either between the two hulls or at the inside of the inner hull, respectively.

What I claim is:

1. In a tanker ship for the transport of liquid products, a safety device to prevent leakage of the stored or transported product comprising an impervious shield means which is flexible in comparison to normal tank bulkheads, said shield means extending along the side of the ships hull in spaced relation thereto so as to delimit the principal cargo space from a vertically extending space along the inner side of the hull, which space is narrow relative to the width of said principal cargo space and open at the bottom region of the ship, said space being intended to contain, when the ship is being used for storage or transport, a liquid having the same or a higher density than the stored or transported product so that the product will communicate with the liquid in the space.

2. A safety device as claimed in claim 1, wherein said shield means is adapted sealingly to connect against cross-wise extending bulkheads dividing the cargo space into adjacent compartments longitudinally of the ship.

3. A safety device as claimed in claim 1, wherein said shield means comprises cloth or fabric such as rubber or plastic fabric.

4. A safety device as claimed in claim 1, wherein said shield means comprises a metal grating having a ground connection to the ship's hull.

5. In a ship in cross-section having its cargo space divided into at least one central principal cargo compartment and two compartments at the sides of the ship, a safety device to prevent leakage of a stored or transported product, said device comprising impervious shield means which are flexible in comparison to normal tank bulkheads, said shield means forming an outer border for the cargo spaces at the lateral sides of the ship so as to define spaces at the inside of the ships hull which are narrow relative to the width of said central principal cargo compartment, said spaces opening in the bottom region of the ship along at least a substantial portion of their length.

6. A safety device as claimed in claim 5, wherein said shield means close to the bottom of the ship extends to said one or several central cargo compartments and/or to the deepest portion of the bottom. 

1. In a tanker ship for the transport of liquid products, a safety device to prevent leakage of the stored or transported product comprising an impervious shield means which is flexible in comparison to normal tank bulkheads, said shield means extending along the side of the ship''s hull in spaced relation thereto so as to delimit the principal cargo space from a vertically extending space along the inner side of the hull, which space is narrow relative to the width of said principal cargo space and open at the bottom region of the ship along at least a substantial portion of its length, said space being intended to contain, when the ship is being used for storage or transport, a liquid having the same or a higher density than the stored or transported product so that the product will communicate with the liquid in the space.
 2. A safety device as claimed in claim 1, wherein said shield means is adapted sealingly to connect against cross-wise extending bulkheads dividing the cargo space into adjacent compartments longitudinally of the ship.
 3. A safety device as claimed in claim 1, wherein said shield means comprises cloth or fabric such as rubber or plastic fabric.
 4. A safety device as claimed in claim 1, wherein said shield means comprises a metal grating having a ground connection to the ship''s hull.
 5. In a ship in cross-section having its cargo space divided into at least one central principal cargo compartment and two compartments at the sides of the ship, a safety device to prevent leakage of a stored or transported product, said device comprising impervious shield means which are flexible in comparison to normal tank bulkheads, said shield means forming an outer border for the cargo spaces at the lateral sides of the ship so as to define spaces at the inside of the ship''s hull which are narrow relative to the width of said central principal cargo compartment, said spaces opening in the bottom region of the ship along at least a substantial portion of their length.
 6. A safety device as claimed in claim 5, wherein said shield means close to the bottom of the ship extends to said one or several central cargo compartments and/or to the deepest portion of the bottom. 